Are we at fault for all bad things?

I would like to know why do we tell “Everything good is from Allah SWT and everything bad is from us.”

If you have already answered this question in your older posts, please provide me the link.

You are referring to verse 4:79, but you should also take verse 4:78, which establishes the context, in order to understand it:

“{4:78} Wherever you may be, death will catch up with you, even if you should be within towers of lofty construction. And if good comes to them, they say, “This is [coming] from God”; and if a bad [thing] hits them, they say, “This is [coming] from you.” Say, “All [things come] from God.” So what is [the matter] with those people that they can hardly understand a statement?

{4:79} What comes to you of good is [caused] by God, but what comes to you of bad is [caused] by yourself. And We have sent you, [O Muhammad,] to the people as a messenger, and sufficient is God as Witness.”

Most translations I read of these two verses fail to distinguish between the two different prepositions that God used here, namely من and من عند, which would lead the English reader to view these two verses as contradictory to each other! 4:78 says that God is the source of all things, good and bad, while 4:79 says that only good things are caused by God while bad ones are caused by us. The distinction specified in the Arabic is lost in the translation and leads to a wrong conclusion! Rather, من عند means “comes from the reservoir of” while من means “is caused by.” Thus, to be faithful to the Arabic, and in doing so dispel confusion, I suggest the above translation.

It is particularly interesting to me that in 4:78, God chastises people for not understanding plain talk. That means that this distinction I explained above was clear enough, yet people did not get it. Indeed, the source of all things is God. Who else is or can be a source? But the cause of something is creature action. If we don’t do the wrong things, nothing wrong will happen! The Sunna (way) of God is that everything is in order, working as planned, in harmony, in precise measure and timing, well designed for maximum benefit. That is why God says that the cause of good is He. God does not do anything to ruin His plan or design. But we often do.

Why are there wars, famine, scarcity, disease, poverty, ignorance, etc., in the world? It is all caused by human action. We are all capable of choosing right, but some of us willingly and knowingly choose the wrong. The result is suffering. That is the cosmic law of cause and effect that God created and set forth.